#include <stdio.h>
#include <stdlib.h>

int factorial(int n);

int main(int argc, char **argv)
{
	int n;
	if(argc < 2) {
		printf("Usage: %s \n", argv [0]);
		return -1;
	}
	else{
		n = atoi(argv [1]);
		printf("Factorial of %d is %d. \n", n, factorial (n));
	}
	return 0;
}
